I think that the very fact the Lennie is shown to be someone who seeks to do the right thing, but ends up being dragged into situations of which he wishes not to be a part is reflective of both his character and the general state of affairs in the novel. Lennie seeks to do the right thing. He follows George's words and does not wish to stray from the path that is laid out in front of him. Yet, Curley seeks to get a rise out of him in confronting him and Curley's wife presents herself to him. In both of these situations, he wishes to do the right thing, but circumstances move him into a dynamic that he is unable to navigate. It is here where I think that Lennie's future in the novel is shown to reside. He will be a character who is immersed in that which he wishes to avoid, making conflict and despair almost inevitable. In this same light, Lennie becomes representative of many of the characters in the novel. They wish for something more, seeking to transcend in what they are. At the same time, these characters are subject to being immersed in that which they don't like and must do what they really don't want to do. This becomes part of Lennie's composition and other characters in the novel.
George tells Lennie to remain quiet, but Lennie forgets these instructions and talks in front of the boss. This foreshadows that Lennie may forget George's directions again in a more serious situation.
Curley antagonizes Lennie and demands that Lennie talk to him. Curley seems to enjoy bullying Lennie. Later, George instructs Lennie to avoid Curley because of Curley's temper and his reputation for fighting. George knows that Curley is a serious threat.
When Lennie admires Curley's wife, George orders him to stay away from her. Lennie's affection for pretty things, and his tendency to accidentally harm his pets, combined with the danger Curley presents foreshadows the tragedy that occurs later.